Shared Line Appearance (SLA) is one of the useful features that have been made available by traditional Private Branch eXchanges (PBXs). SLA has also been referenced as CO line, key system emulation, and the like. In essence, SLA is a feature that maps the line appearance (or a function key, button, etc.) on a phone to an analog port or a co-line or simply “the trunk.” When a specific co-line is mapped to multiple phones, the activity of that line can be monitored and/or used by each phone. Thus, if “line 1” is busy, everyone that has their phone mapped to “line 1” can see that the line is busy. Likewise, if multiple users have their phones mapped to “line 1”, then each user's phone will ring for an incoming call to “line 1.” This means that any of the mapped users (e.g., users sharing the common line appearance) can pick up a call coming to “line 1.” Moreover, a user can place a call on hold to “line 1” and any other user can pick up the same call from hold by connecting to “line 1” through the SLA feature. With SLA any user can join a call that has already been answered by another user sharing the common line appearance.
With SLAs, one person may not want to actually share credentials (e.g., login information, user names, passwords, etc.) with other users of the SLA. However, each user may have different call preferences or restrictions that require different applications to be sequenced for each user.
Other types of features that are currently provided by PBXs include Bridged Call Appearances, Hunt Groups, Coverage Answer Groups, Calling Groups, and Call Pickup Groups. These features also experience complications when different users belonging to such groups desire to have their call preferences or restrictions invoked.